1. Field of the Invention
The present invention relates to a vehicle headlamp of the type in which a discharging bulb is used for its light source.
2. Related Art
There is a recent demand of discharge bulbs because the bulbs are good in luminance efficiency and color rendering property, and long in lifetime. The study has actively been made on the application of the discharge bulb as a light source of the headlamp for motor vehicles.
In order to activate the discharging operation of the discharge bulb, a starter circuit must be used which applies a high tension between the opposed electrodes of the discharge bulb. When a switching element for generating high tension pulses is driven and the discharge bulb discharges, electromagnetic waves are generated, and cause noise harmful to other electrical parts assembled into the automobile.
A measure for addressing the electromagnetic waves emitted from the discharge bulb is to form a conductive layer on the lamp body to prevent the electromagnetic waves from leaking out of the lamp. A measure for addressing the electromagnetic waves emitting from the starter circuit is to put the starter circuit in a conductive metal case to confine the electromagnetic waves within the metal case.
The above-noted measures can effectively interrupt the electromagnetic waves emitted from the discharge bulb and the starter circuit, but cannot interrupt the electromagnetic waves emitted from a power cable connecting the starter circuit to the discharge bulb and a connection part between the power cable and the discharge bulb.